• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.3 s.357
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• pp.98-104
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• 2007

In this paper, the dual-band open loop antenna using a strip conductor for the RFID reader and Wireless LAN Application, which has a resonant frequency at 910MHz and 2.45 GHz, is proposed. Input impedance of antenna is matched with the feed line of 50 ohm by varying the length and width of sip conductor making up the antenna. The gain and directivity of antenna is enhanced as tuning the length of strip, and as also grooving the teeth shapes on the strip conductor. The size of fabricated antenna is $75mm\times100mm$. The return loss and the gain of fabricated antenna are -11.92 dB, 3.02 dBi at 910 MHz and -21.31 dB, 4.08 dBi at 2.45 GHz, respectively.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.6
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• pp.504-511
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• 2003

In this paper, inverter type neon power supply using a piezoelectric transformer is fabricated and its characteristic is investigated. Developed neon power supply is composed of basic circuit and blocks, such as rectifier part, frequency oscillation part and piezoelectric transformer and resonant half bridge inverters. In this paper for complement the low power limitation, piezoelectric transformer at parallel connected driving by inverter is studied for noon tubes system of high power. When piezoelectric transformer is connected with parallel, LC filter connection method with parallel and selection of inductance L and capacitor C of primary side is suggested for reduce unbalanced current at the terminal of each transformer. Piezoelectric transformers use piezoelectric ceramic devices. Thus it is wireless therefore it has high power density, high Isolation level, low loss, more light, and miniaturization. In addition, high voltage transfer ratio is expected because there is no leakage inductance. Also, it has economic merit that the electrical loss Is low because structure is simple, small and tighter weight.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.10-16
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• 2021

This paper proposes a model that considers the parity-time symmetric structure as a state detection circuit for sensor applications using a stretchable inductor. In particular, to obtain a more practical computer simulation result, the stretchable inductor model was applied to this study model by referring to previously reported experimental results. The resistance component and phase component were controlled through the negative differential resistance circuit used in this study. In addition, the imbalance of the circuit caused by a change in the characteristics of the stretchable inductor could be compensated for using a negative differential resistance circuit. In particular, an analysis of the frequency characteristics of the sensor driving circuit of the parity-time symmetric structure proposed in this study confirmed that the Q-factor could be increased up to 20 times compared to the conventional resonant circuit.

• Progress in Superconductivity
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• v.14 no.1
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• pp.45-51
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• 2012

Microwave metrology for the thickness of metallic or superconductive films provides a new way to measure the film thickness in a non-invasive way by using microwave resonators, with the measurement accuracy affected by standard uncertainties in the resonator quality factor, temperature-dependent resonant frequency and the dimensions of the resonators. Here we study effects of the standard uncertainty in the thickness, $t_{cal}$, of a calibration $YBa_2Cu_3O_{7-{\delta}}$ (YBCO) film on the measured thicknesses, $t_{RF}$, by using a ~ 40 GHz microwave resonator. For the study, we used five YBCO films having the thicknesses of 70 - 360 nm, for which relative standard uncertainties in $t_{RF}$ due to that in $t_{cal}$ are obtained. The standard uncertainty in $t_{cal}$ was determined with the surface roughness of the film taken into account. It appeared that relative standard uncertainty in $t_{cal}$ significantly affects the $t_{RF}$ values, with the values of 1% (5%) in the former resulting in those of 1-2% (5-9%) for the latter at 10 K. Our results show that, for realizing relative standard uncertainties less than 5% in $t_{RF}$ for all the YBCO films, the surface roughness of the calibration films should be small enough to realize a relative standard uncertainty of less than 2.7% in $t_{cal}$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.6A
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• pp.648-656
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• 2007

This paper is about band pass filter, using Ceramics in the condition of center frequency 370Hz at milli-wave. The band pass filter is applied to Broadband Convergence Network, representing WLL(Wireless Local Loop) and LMDS(Local Multi-point Distribution Service). Sticking ceramic between strip line on a dielectric material substrate with which conductor's covers upper and basal surface, One will house the exterior by using structural resonance. In this Non Radiative Microstrip Line Filter structure, based upon simulations, generalized the two formulas finding resonant frequency of 1step ceramic resonator and bandwidth of 4step ceramic resonator. Also, As a result of experiment, using Network Analyzer, about created a experiment of structure based on the simulation result of 4-step ceramic resonator, It showed good characteristic of targeted bandwidth, comparing simulated result of 36.58GHz$\sim$37.650GHz with experimented result of 36.6GHz$\sim$37.65GHz.

• Journal of Advanced Navigation Technology
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• v.17 no.6
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• pp.646-651
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• 2013

In this paper, a small inverted-F antenna with adjustable characteristics is proposed with use of lumped elements, capacitor and resistor. Capacitor is inserted between end of the antenna and ground for size reduction and tuning of resonant frequency. On the other hand, $0{\Omega}$ resistor is replaced as the short line connected to ground. The movement of short point due to use of $0{\Omega}$ resistor results in providing variation of input impedance. Therefore optimum characteristics can be obtained only by proper choice of capacitor and short point without redesign of it's geometry. In order to check the validity, the proposed antenna is designed and fabricated for 2.4 GHz frequency band, and then is applied to a product of Zigbee wireless remote controller. As a result, the size of applied antenna is $8.5{\times}4.5mm^2$ and it is observed that the measured bandwidth and antenna gain are 150 MHz and 2 dBi respectively without redesign of the antenna.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.11
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• pp.1128-1134
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• 2014

In this paper, the effects of a metamaterial slab with negative permeability in a magnetically coupled wireless power transfer system (WPT) in the overall performance are analyzed quantitatively in terms of the effective quality factors of the loop resonators and coupling coefficient considering the slab losses, based on an equivalent circuit. Using the ideal metamaterial slab(lossless slab), the WPT efficiency is improved considerably by the magnetic flux focusing. However, the practical lossy slab made of RRs or SRRs limits the significant enhancement of WPT efficiency due to the relatively high losses in the slab consisting of RRs or SRRs near the resonant frequency. For the practical loop resonator, other than a point magnetic charge, using the practical lossy metamaterial slab in order to improve the transfer efficiency, the width of the slab needs to be optimized somewhat less than the half of the distance between two loop resonators. For the low-loss slab with its loss tangent of 0.001, the WPT efficiency is maximized at 93 % when the ratio of the slab width and the distance between the two resonators is approximately 0.35, compared with 53 % for the case without the slab. The efficiency in case of employing the high-low slab(loss tangent: 0.2) is maximized at 61 % when the slab ratio is 0.25.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.1273-1278
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• 2005

In this thesis, a 2 stage 6-pole bandpass filter(BPF) is designed and implemented by using triple-mode cavity for satellite payload system. The BPF has a 100MHz bandwidth at the center frequency of 14.5GHz(Ku-band) and the response of the filter is the Chebyshev function. The cavity filter uses two orthogonal $TE_{113}$ modes and one $TM_{012}$ mode. The coupling between the adjacent cavityes(intercavity coupling) results in a Chebyshev response and is accomplished by only H-filed component of TE modes. The size and location of intercavity slot is determined by the coupling equation from E- and H-field of TE and TM resonant modes in circular cavity. The 2-stage 6-pole triple-mode cavity BPF has the insertion loss of 2.4dB and the reflection loss of 15dB in the passband. The triple-mode BPF proposed in this thesis can be used as channel filters for satellite payload system and can minimize filter assembly in general wireless communication system.

• Journal of the Korean Ceramic Society
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• v.40 no.4
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• pp.350-353
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• 2003

Millimeter-wave dielectric ceramics have been used like applications for ultrahigh speed wireless LAN because it reduces the resources of electromagnetic wave, and Intelligent Transport System (ITS) because of straight propagation wave. For millimeterwave, the dielectric ceramics with high quality factor (Q$.$f), low dielectric constant($\varepsilon$), and nearly zero temperature coefficient of resonant frequency ($\tau$) are needed. No microwave dielectric ceramics with these three properties exist except Ba(Mg$\_$1/3/Ta/sub1/3/)O$_3$ (BMT), which has a little high s: In this paper, alumina (Al$_2$O$_3$) and fosterite (Mg$_2$SiO$_4$), candidates for millimeter-wave applications, were studied with an objective to get high q$.$f and nearly zero $\tau$$\_$f/ For alumina ceramics, q$.$f more than 680,000 GHz was obtained but it was difficult to obtain nearly zero Qf. On the other hand, for forsterite ceramics, q$.$f was achieved from 10,000 GHz of commercial for sterite to 240,000 GHz of highly purified MgO and SiO$_2$ raw materials, and $\tau$$\_$f/ was reduced a few by adding TiO$_2$ with high positive $\tau$$\_$f/.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.9
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• pp.41-45
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• 2014

In this paper, a high-efficiency power amplifier is implemented by using a drain bias control circuit operated at low input power for WPT(Wireless Power Transfer). Adaptive bias control circuit was added to high-efficiency class-E amplifier. It was possible to obtain the overall improvement in efficiency by adjusting the drain bias at low input power. The proposed adaptive class-E amplifier is implemented by using the input and output matching network and serial resonant circuit for improvement in efficiency. Drain bias control circuit consists of a directional coupler, power detector, and operational amplifier for adjusting the drain bias according to the input power. The measured results show that output powers of 41.83 dBm were obtained at 13.56 MHz. At this frequency, we have obtained the power added efficiency(PAE) of 85.67 %. It was confirmed increase of PAE of an average of 8 % than the fixed bias from the low input power level of 0 dBm ~ 6 dBm.